The invention described herein arose in the course of, or under, Contract No. DE-AC08-83NV10282 between the United States Department of Energy and EG&G Energy Measurements, Incorporated.
This invention relates to a process for producing high purity mercuric iodide. More particularly, this invention relates to a process for producing high purity mercuric iodide by passing a vapor of a mercuric compound through a low vapor pressure particulate bed of an iodide compound to form mercuric iodide.
High purity mercuric iodide (HgI.sub.2) is valuable as an ambient temperature radiation detector for electromagnetic radiation ranging from visible light up through x-ray and gamma ray wavelengths. When crystal quality is high enough, HgI.sub.2 may be used in the manufacture of spectrometers. However, high quality crystals require extremely pure HgI.sub.2.
Schieber et al U.S. Pat. No. 4,030,964 teaches the production of HgI.sub.2 crystals by vapor phase growth in a two stage horizontal furnace wherein purified HgI.sub.2 material is placed into one end of an ampoule and sublimed in one zone of the furnace and then grown as a crystal in an opposite end of the ampoule located in a second cooler zone of the furnace. However, the patentees require a purified HgI.sub.2 as a starting material.
It is also known to grow HgI.sub.2 with electrical properties suitable for use as nuclear radiation detectors by a chemical transport method using organic materials. Faile U.S. Pat. No. 4,282,057 describes such a method for producing a low temperature red form of mercuric iodide using styrene, polyethylene, or a CN-containing reagent such as NH.sub.4 SCN or Hg(SCN).sub.2. Mercuric iodide and the reagent are placed in one end of a sealed evacuated tube which is then heated while the other end of the tube is maintained at room temperature resulting in the growth of mercuric iodide platelets at the cooler end of the tube.
However, hydrocarbons appear to be one of the worst contaminants to remove from HgI.sub.2 when it is desired to provide the high purity HgI.sub.2 needed for high quality crystals. It would, therefore, be desirable to provide a process for the production of high purity HgI.sub.2 without the necessity of removing hydrocarbons from the HgI.sub.2 to achieve such purity.